Cerebrotendinous xanthomatosis is a rare autosomal recessive lipid-storage disease caused by a mutation in the sterol 27-hydroxylase (CYP27) gene1,2. It is important that orthopaedic surgeons be aware of this condition because the initial presentation may be symmetric, painful enlargement and deformity of the Achilles tendons. Early diagnosis is the key to treatment because medical therapy is effective in halting progression of, although not reversing, the devastating neurological lesions of this condition.